Sierra Nevada frog likes a cool climate

The Sierra Nevada yellow-legged frog, one of the moister creatures on the planet, is the poster amphiban for the dire effects of climate change in high mountains..

Once the most abundant vertebrate in the Sierra, now they’re on the brink of extinction. Snowmelt in the Sierra is expected to be reduced by half in the coming decades, drying up the shallow lakes needed by the tadpoles to survive.

The frogs, previously named mountain yellow-legged frogs, used to live as low as 6,000 feet. Scientists believe that pesticides coming from the Central Valley and the invasive trout stocked for anglers very likely wiped them out. Now the frogs are found only above 9,000 feet along with other creatures threatened by climate change, the Yosemite toads, Pacific treefrogs and garter snakes.

Researchers stake out a High Sierra lake.

And now global warming looms as a problem for the amphibians and reptiles. Climate change models forecast a decreased snow pack with a reduction of more than half of the melted water by 2090. Over the last 10 years, there have been some high snow-pack years and some low snow-pack years when the lakes dried up. “As climate warms, the models suggest that low snow-pack years will be more common, said Kathleen R. Matthews, coauthor and scientist at the Forest Service’s Sierra Nevada Research Center.

In the warming years, when the small lakes dry up, the tadpoles die, even the ones that have been in that lifecycle stage for three or four years. “When tadpoles die, you’re not going to get any new frogs coming into the population,” said Matthews.”

There are large lakes in the High Sierra where the frogs bred for thousands of years. But California Department of Fish and Game started stocking them with the non-native trout in the 1950s. The lakes never before had fish, even native ones. The stocked fish became predators for frog eggs and tadpoles, and have killed off much of the population. In the late 1970s, the federal officials stopped the stocking in the national parks. Only in the last month, a lawsuit filed by environmental groups stopped Fish and Game from stocking the hatchery fish as a way to save imperiled native fish and amphibians. The order is temporary while the agency completes a full environmental review of the effects of the stocking program.

The climate models predict that there would be even a more dramatic changes in the snowpack at lower elevations, also affecting species there, including the American pika and amphibians and reptiles.

Igor Lacan, formerly at the Forest Service and now a post-doctoral scientist at UC Berkeley’s Department of Environmental Science.